Cavity-Enhanced Photon Emission from a Single Germanium-Vacancy Center in a Diamond Membrane

The nitrogen-vacancy (NV) center in diamond has been explored extensively as a light-matter interface for quantum information applications, however it is limited by low coherent photon emission and spectral instability. Alternatively, group-IV diamond defects such as the germanium-vacancy (GeV) center have gained attention for their superior optical properties. Inspired by this, we explore an interface based on a single GeV in a diamond membrane coupled to a finesse 11,000 fiber cavity, obtaining a 30-fold enhancement in the spectral density of emission. This work sets the stage for cryogenic experiments, where we predict a factor of 20 increase in the spontaneous emission rate.